A method of providing a layer of non-polar (also called hereafter “hydrophobic”) liquid on a surface of a substrate, particularly suitable for making electrowetting displays, is known. The surface is initially covered by a layer of polar or conductive (also called hereafter “hydrophilic”) liquid. A dispenser has its opening positioned inside the polar or conductive layer and above the surface. Non-polar liquid is fed into the dispenser and a drop of non-polar liquid is formed between the opening and the surface. The surface includes first hydrophobic areas surrounded by second hydrophilic areas. When the dispenser moves over the surface, the drop of non-polar liquid is dragged over the first and second areas and replaces the polar or conductive liquid on the first areas by a layer of non-polar liquid while leaving the polar or conductive liquid on the second areas.
A disadvantage of the known method is that it requires process equipment specifically developed for filling electrowetting devices. Another disadvantage of this method is that the method is relatively slow and is difficult to scale up to large size substrates. Another disadvantage of this method is poor productivity caused by the fact that a cover glass is attached in a liquid after formation of the hydrophobic liquid layers.
Another method is known in which a container having a liquid inlet and a liquid outlet is prepared; first and second liquids, one having conductivity (hydrophilicity) and the other having non-conductivity (hydrophobicity) are prepared; the first liquid is fed into the container and then the second liquid is fed thereinto; and thereby an interface is formed between the first and second liquids. In this method, however, the hydrophobic liquid coagulates at one portion to cause unevenness.
It is desirable to provide a method that allows use of existing equipment for filling or provide a method that is much faster or significantly more scalable than known methods.